This invention relates to broadband radio frequency communication systems and methods and more particularly to a system and method which provides for broadband information communication between processor-based systems through a centralized communication array.
In the past, information communication between processor-based systems, such as local area networks (LAN) and other general purpose computers, separated by significant physical distances has been an obstacle to integration of such systems. The choices available to bridge the physical gap between such systems have not only been limited, but have required undesirable tradeoffs in cost, performance, and reliability.
One group of historically available communication choices includes such solutions as the utilization of a standard public switch telephone network (PSTN) or multiplexing signals over an existing physical link to bridge the gap and provide information communication between the systems. Although such solutions are typically inexpensive to implement, they include numerous undesirable traits. Specifically, since these existing links are typically not designed for high speed data communication, they lack the bandwidth through which to communicate large amounts of data rapidly. As in-building LAN speeds increase to 100 Mbps, the local PSTN voice grade circuits even more markedly represent a choke point for broadband metropolitan area access and therefore are becoming a less and less desirable alternative. Furthermore, such connections lack the fault tolerance or reliability found in systems designed for reliable transmission of important processor-based system information.
Another historically available group of communication choices is found at the opposite end of the price spectrum than those mentioned above. This group includes such solutions as the utilization of a fibre optic ring or point to point microwave communication. These solutions are typically cost prohibitive for all but the larger users. The point to point systems require a dedicated system at each end of the communication link which lacks the ability to spread the cost of such systems over a plurality of users. Even if these systems were modifiable to be point-to-multipoint, to realize the economy of multiple system use of some system elements, the present point-to-point microwave systems would not provide broadband data services but rather traditional bearer services such as T1 and DS3. Furthermore these systems typically provide a proprietary interface and therefore do not lend themselves to simple interfacing with a variety of general purpose processor-based systems.
Although a fibre optic ring provides economy if utilized by a plurality of systems, it must be physically coupled to such systems. As the cost of purchasing, placing, and maintaining such a ring is great, even the economy of multi-system utilization generally does not overcome the prohibitive cost of implementation.
A need therefore exists in the art of information communication for a communication system providing cost effective bridging of large physical distances between processor-based systems.
A further need exists in the art for a communication system providing high speed broadband information communication between processor-based systems.
A still further need exists in the art for a fault tolerant communication system providing reliable bridging of physical gaps between processor-based systems.
Additionally, a need exists in the art for a broadband communication system providing simple connectivity to a variety of processor-based systems and communication protocols, including general purpose computer systems and their standard communication protocols.
These and other objects, needs and desires are obtained in a system and method of communication in which a communication array, or hub, is centrally located to provide an air link between physically separated processor-based systems, or other sources of communication such as voice communication, utilizing a communication device, or node, of the present invention. Preferably, this central array may be physically coupled to an information communication backbone providing communication between air linked systems and physically linked systems. Furthermore, multiple ones of such system may be utilized to bridge large physical separation of systems by the intercommunication of multiple central arrays. Moreover, pervasive surface coverage may be provided by arranging a plurality of such communication arrays to provide a cellular like overlay pattern.
In a preferred embodiment, the central communication array comprises a plurality of individual antenna elements in time division multiplex (TDM) communication with a processor-based system. This system processes signals received at each antenna element in order to route them to their desired destination. An advantage of using a plurality of individual antenna elements at the central communication array is that only antenna elements having a radiation pattern overlaying a remote site requiring communication service (subscriber) need be implemented at any particular time. Thereafter, as more subscribers require service by a particular hub, additional antenna elements may be installed. This modular expansion of the service capabilities of a hub results in reduced initial installation costs where only a few subscribers initially require service, while maintaining the flexibility for implementation of omni directional and/or cellular overlay communication coverage not possible with point-to-point systems.
Also in a preferred embodiment, the communication spectrum utilized by the communication system is frequency division multiplexed (FDM) to provide multiple channels for simultaneous information communication to a plurality of subscribers. In addition to simultaneous information communication to the subscribers, FDM channels may also be used to communicate control information through a predetermined band to network elements simultaneously with the transmission of other data.
Preferably a carrier frequency in the millimeter wavelength spectrum, such as 10 to 60 GHz, is used by the present invention. Such carrier frequencies are desirable in order to provide a communication bandwidth sufficient for the transmission of at least 30 Mbps through each defined FDM channel of approximately 10 MHZ.
The FDM channels may provide full duplex by defining a transmit (Tx) and receive (Rx) channel pair as a single frequency division duplex (FDD) channel to serve a subscriber. However, it shall be appreciated that the provision of full duplex by FDD is at the expense of depletion of the available spectrum at an increased rate as service to a single subscriber actually requires two channels.
In addition to multiplexing communication on frequency divided channels, time division multiplexing may be utilized to provide multiple, seemingly simultaneous, communications on a single FDM channel. Here ones of the FDM channels are broken down into a predetermined number of discrete time slices (burst periods) which form a frame. Each burst period may be utilized by a different subscriber so as to result in information communication contained in a single frame, having a number of TDM bursts, being directed to/from a number of subscribers over a single FDM channel.
Moreover, full duplexing may be synthesized on a single FDM channel by time division duplexing (TDD) through the use of burst periods like those used in TDM. Through TDD, Tx and Rx frames, each frame having one or more burst periods, are defined to provide communication in a particular direction at a predefined time.
It shall be appreciated any of the aforementioned FDM, FDD, TDM, and TDD schemes, or their like, may be utilized in any combination deemed advantageous. For example, a single frequency division channel may be time division multiplexed to provide communication to a number of subscribers while simultaneously being time division duplexed to synthesize full duplexed communication with these subscribers.
In the above described embodiments, the communication system may utilize an initialization algorithm, perhaps including a token passing arrangement for shared data users, to poll subscriber""s systems and determine communication attributes of each such system at each antenna element of the central array. This information may be utilized to determine the optimum assignment of resources, including antenna elements, TDM burst periods, FDD frequency assignments, and TDD Tx and Rx time assignments for each such system. This information may additionally be utilized to provide secondary assignment of resources to maintain system integrity in the event of an anomalous occurrence, thereby providing system fault tolerance.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter, which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.